Method of making a magnetic hybrid interleaved head

ABSTRACT

An interleaved head for reading and writing data transitions onto a magnetic tape. A magnetic recording system for the bi-directional transportation of the tape media across the interleaved head. A controller controls the tape drive in a reel-to-reel format to accomplish the bi-directional motion of the tape media. The interleaved head includes two modules with each module having a plurality of alternating read and write transducers alternately spaced apart along a single line placed transverse to the movement of the magnetic tape. The two modules are placed together such that the write gaps of one module are aligned with the read gaps of the other module. Each read module includes the magneto-resistive element. Each write transducer includes a thin film conductor driving a nickel zinc ferrite substrate as one pole piece and a nickel zinc closure piece as the second pole piece. In order to provide leveling across the write transducers of the module, write back gap islands are provided in the back gap regions of the write transducer made of the same material with the same thickness as the magneto resistive element and the conductors interconnecting the magneto resistive element to the read/write network of the tape drive.

TECHNICAL FIELD

This invention relates generally to the field of magnetic recording, andmore specifically to a drive wherein the magnetic media carries multipleparallel channels of data and to a transducer operable to sense themagnetic transitions from the media.

BACKGROUND OF THE INVENTION

Tape drives that operate bi-directionally are well-known. The tape mediais generally enclosed into a single reel cartridge and the tape istransported around the tape path onto a tape reel thereby placing thetape media in contact with the transducer. The transducer in present daytape drives comprise a separate read and write element that cover eachtrack of the data on the tape media. It is known, for instance, that aone-half inch wide magnetic tape can include 18 tracks. A higher numberof tracks are contemplated and it is proposed that a one-half inch widemagnetic tape includes 36 tracks. To be able to read 36 tracks from thetape, an interleaved data transducing head is proposed.

An interleaved read/write head is disclosed in U.S. Pat. No. 4,685,005to Fields, and assigned to the assignee of the present invention. In themagnetic head disclosed in that patent, the read and write gaps of eachmodule of the magnetic head are alternately spaced across the width ofthe tape, such that the write gaps of one module are aligned with theread gaps of the other module. When one module is selected for writing,as a function of the direction of the tape movement, the other module isselected to read-after-write check the data written by the write elementof the first module. One module writes odd track data during onedirection of the tape movement and reads even track data during theopposite direction of the tape movement. The problem arises in that bothread and write elements are located within one module with the gaps ofeach element aligned along the same line.

The read element of the modern day tape head is a magneto-resistivetransducer and is formed of thin film layers deposited through astandard thin film deposition procedure. The write transducer, however,has its pole pieces formed from two blocks of magnetic ferritemagnetically connected together at the back gap and a transducing gap atthe front face. A single block of magnetic ferrite operates as a closurestructure after all of the elements of the read transducer and the writeconductors are deposited onto the substrate magnetic ferrite block.Having different layers of material deposited at different locationsinto the side-by-side elements creates a leveling problem when themagnetic ferrite closure block is to be placed over the plurality ofread and write elements. More layers form a greater thickness in theread element and therefore the write element generally lacks asupporting structure that can cause the magnetic ferrite closure pieceto bend under stress when affixed to the completed transducers. In anyevent, the write head gap must not be narrower than the read head gap toproperly read the written bits of information onto the magnetic media.Also, with the closure piece bent under stress at the time ofmanufacture, the stress may relieve in time, resulting in an unreliablegap.

It is, therefore, an object of the present invention to provide anenhanced magnetic recording drive for multi-track operation.

Yet another object of the present invention is to provide a magneticdrive that uses an enhanced interleaved head to read and write magnetictransitions forming data onto magnetic recording media.

Another object of the present invention, therefore, is to provide anenhanced transducer assembly and an enhanced method for making thetransducer assembly.

SUMMARY OF THE INVENTION

The present invention provides a bi-directional media drive which usesan interleaved transducing head that solves the mechanical and magneticproblems between the gap lengths of the read and write elements.

The magnetic interleaved head according to the present inventionincludes two data transducing head modules. Each of the head modulesinclude one transducing gap line extending normal to the movement of themedia. Each gap line includes a plurality of alternating write and readgaps. Each of the head modules includes a substrate made of a magneticferrite material. An insulating layer is deposited onto the substrate toprepare for the deposition of the read element films and the writeconductor. A patterned magneto resistive layer forming the readtransducer is then deposited onto the insulating layer. The magnetoresistive layers also form read, write and back gap write islandsadjacent to the read elements and adjacent to the proposed writeelements. A patterned conductor layer is deposited on each magnetoresistive layer to connect the magneto resistive portion of the readtransducer for interconnection to the rest of the media drive. Thepattern conductor layer is also deposited over the islands, namely, theread, write and back gap write islands. A patterned second insulatinglayer is deposited on each conductor layer such that the write track andthe read leg regions are exposed. A read and a write conductor isdeposited into each patterned write track region and read leg region. Aread and a write interconnecting layer is deposited to connect each readand write conductor to the media drive, namely the data transmittingmeans which writes the magnetic transitions onto the media and senses orreads the written magnetic transitions from the media for use by thedrive and the connecting data processing system. A magnetic ferriteclosure piece covering all of the plurality of alternating write andread gaps of the head is affixed over the preceding layers. The magneticferrite closure forms one write pole piece and a read gap shield for themagneto-resistive read element while the substrate provides the secondwrite pole piece. The read, write and back gap provide the mechanicalsupport for the magnetic ferrite closure piece to produce a correctwrite gap length.

The media drive of the present invention, therefore, comprises aninterleaved transducer as just described and means for moving the mediapast the interleaved transducer. The drive further includes means fortransmitting the data to and receiving the data from the interleavedtransducer.

By depositing an island of the read transducer material and the readconductor materials in the front and back gaps of the write track regionand also in front of the read element in the read section, the filmlayers in both the read and write sections produce the same height inthe various depositions. Therefore, when the closure is assembled tocomplete the head module, the gap length of the read and writetransducers will be essentially the same, and no bending of the closurewill occur.

In the present invention, therefore, the supporting structure of onemodule of a magnetic head having alternating read and write elementsincludes supporting islands adjacent each of the shorter lengths ofeither the write or read gaps. In the instant that the write gap lengthsare shorter, the islands are placed adjacent each write element. In theinstant that the read gap lengths are shorter, the islands are placedadjacent each read element. The supporting structure is preferablymagnetic ferrite but could be a non magnetic ceramic. The supportingislands could be made of magnetic materials to enable the independentvariations of the magnetic properties of the read or write gapscontaining the islands, or the supporting islands could be made of thesame materials that comprise the layers of the longer gap lengthelement.

An object of the present invention, therefore, is to provide a mediadrive that includes an enhanced interleaved magnetic head.

Another object is to provide an interleaved head that minimizes thebending stress in the closure and hence provide a more stable andreliable length.

Still another object is to provide an interleaved head that has the readand write gap essentially of the same length.

Yet another object of the present invention is to provide an interleavedhead for magnetic drives that includes islands of the material used inthe formation of the read element in the front and back gap of the writeelement region and also in front of the read element in the read sectionsuch that the read and write sections are of the same height when theclosure module forming the second pole piece of the write element isassembled over the module.

These and other objects of the present invention will become apparent tothose skilled in the art as the description proceeds.

BRIEF DESCRIPTION OF THE DRAWINGS

The various novel features of this invention, along with the foregoingand other objects, as well as the invention itself both as to itsorganization and method of operation may be more fully understood fromthe following description of illustrated embodiments when read inconjunction with the accompanying drawings, wherein:

FIG. 1 is a schematic of a tape drive and controller useful with themagnetic head according to the present invention;

FIG. 2 is a top view of a length of magnetic tape and its relationshipto an interleaved head; and

FIG. 3 is a sectional view of a portion of an interleaved head of thepresent invention;

FIGS. 4A-C are the mask drawings used to deposit the different layersforming several tracks of the interleaved head; and

FIG. 5 is a perspective view of a portion of the transducers produced bythe steps of FIGS. 4A-C, showing the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The present invention is preferable for use in an interleaved magnetichead. The interleaved magnetic head has its use to read and writemagnetic transitions from a multi-track recording media. This in turnfinds its major usage in tape drive systems. A typical tape drive systemwell known today is the IBM 3490 tape drive. In a tape drive system, thetransducer generally remains fixed and the tape is moved across thetransducer in both directions to read and write from various transducersin the magnetic head to record data information onto at least one of aplurality of tracks on the media. The interleaved head is of particularimportance since the number of tracks can be increased while stillproviding the bi-directional operation of the media while alsopermitting an immediate read back check of the data just written ontothe tape media. A schematic view of the entire tape drive systempreferred in the embodiment of the present invention is shown in FIG. 1.Reference is made to the U.S. Pat. No. 4,125,881 to Eige, et al. andassigned to the assignee of the present invention for a more completedescription of a control circuit usable for a reel-to-reel tape drive.Only the apparatus and procedure for an understanding of the presentinvention is given herein.

As shown in FIG. 1, a controller 10 accepts information from a supplyreel tachometer 12 which is connected to a supply reel motor 14. Thesupply reel motor 14 is driven by a motor drive circuit 23 to reversiblyrotate a supply reel 16 shown located within a single reel cartridge16A. The tachometer 12 directs count pulses to a counter 19 to indicatethe number of rotations and the rotational position of the motor 14 andthe supply reel 16. The output of the counter 19 is directed to acontrol unit 17. Another input to the control unit 17 is via the counter19 that accepts count pulses from a take up reel tachometer 20. Thetachometer 20 is connected to a take up reel motor 22 that is reversiblydriven by the motor drive 23 which applies torque under the control ofthe control unit 17. The motor 22 drives a take up reel 24. A timer 26is connected to the control unit 17 in the controller 10 to control theapplication of a motor drive 23 power to the motors 14 and 22.

A magnetic tape 28 and its leader block 29 takes a path, shown by adotted line 27, from the supply reel 16 to the take up reel 24 past anidler bearing 30, air bearing tape guides 32 and 34, and a magnetic head36. The tape path 27 continues around a roller 38 of the tension armtransducer 18 to the take up reel 24. An example of a tape drive forthreading the leader block 29 and the tape 28 through the complex tapepath 27 is disclosed in U.S. Pat. No. 4,335,858 assigned to the assigneeof the present invention. The transducer 36 is preferably an interleavedmagnetic head such as is disclosed in the U.S. Pat. No. 4,685,005 toFields The disclosure in both of these Patents is incorporated herein byreference for a more detailed description of the preferred embodiment.

The output of the magnetic head 36 is connected to a read/write network15. The read/write network 15, under control of the control unit 17,directs data to a data unit 13 in the read format, and accepts data fromthe data unit 13 when data is to be written onto the tape 28 by themagnetic head 36. The data unit 13 is generally connected to a centralprocessing unit (CPU) which also controls the operation of the controlunit 17. FIG. 2 shows a top view of the interleaved magnetic headaccording to the present invention.

The head to be used in the practice of the present invention can alsotake the form of any of a number of well known construction types andarrangements. However, thin film construction is preferred. By the useof photolithography, it is possible to maximize use of the surface ofthe media, since narrow, closely placed, tracks can be written. Thepresent invention provides the advantage that transversely adjacent headelements are not operative at the same time, thus minimizing thepossibility of cross-talk and the like. In the preferred embodiment of athin film transducer used for the magnetic head 36, the write element isan inductive write element comprising two blocks of magnetic ferritedriven by a thin film coil formed by the standard photolithographicsteps. The preferred read element is a magneto-resistive (MR) element.It is also preferred that such MR read gaps be of the soft film biasedtype, well-known to those skilled in the art. It is also preferred thatthe head construction implement the well known write-wide read-narrowformat.

Referring now to FIG. 2, the read elements are marked R for the magnetichead 36 while the write elements are marked W. The read and write gapsare used in immediately alternating, odd/even fashion. The termalternating is intended to include other formats. For example, it is thepreferred embodiment of the present invention to provide a format of 36tracks across the width of the media, hereinafter called tape media. Oneformat provides that the odd numbered tracks, tracks 1, 3, 5, and soforth are operative during forward tape movement, while the even numbertracks 2, 4, 6, 8 and so forth are operative during the oppositedirection of the movement of the tape media. Other formats useful in thepractice of the present invention will of course be evident to those ofskill in the art, and are considered to be within the teaching of thepresent invention. The same reference numerals indicate like structuralfeatures and operations in the various figures of the drawings.

In general, referring to FIG. 2, the length of magnetic tape 28 moves inboth a forward and a reverse direction as indicated by the arrows 40 and42. The arrow 40 designates the forward movement direction of the tape28 and the arrow 42 designates the reverse direction. The magnetic tape28 operates in transducing relationship with the magnetic head 36 in thestandard well-known format. The magnetic head 36 includes two modules 44and 46 of generally identical construction. These two modules aremounted together to form a single physical unit. In this manner, thetransducing gaps of one module are not only closely spaced to thetransducing gaps of the other unit, but also, the module gaps areaccurately aligned in the direction of tape movement.

In the exemplary magnetic head 36 of FIG. 2, each module includes onegap line 48 and 50 of modules 44 and 46, respectively, to form thesingle physical unit of magnetic head 36. The individual gaps of eachmodule are accurately located along the gap lines 48 and 50. As thoseskilled in the art will appreciate, it is essential that gap lines 48and 50 be parallel, and that the head be mounted to the tape drive, asshown in FIG. 1, in an accurate manner such that the gap lines 48 and 50are perpendicular to the direction of tape media movement as representedby the arrows 40 and 42. The magnetic head 36 includes the alternatingread/write gaps along the length of each of the gap lines 48 and 50 foreach of the modules 44 and 46. There are 18 read transducers and 18write transducers in each of the modules 44 and 46. Magnetic tape 28,therefore, has 36 tracks across its one half inch width. The tracks arewritten about 35 percent wider than the read gaps are able to read. Thegaps of one module, module 44 for instance, cooperate with theidentically numbered gaps of the module 46. Thus the gaps identified as"1" through "36" of module 44 cooperate with the gaps identified as "1"through "36" of the module 46. The read gaps of one module are alignedwith the write gaps of the other module. Thus a write gap 52 of module44 is aligned with a read gap 54 of the module 46. The write gap 52writes a 35 percent wider track 1 onto the magnetic tape 28 and thistrack 1 is then read by the read gap 54 of the module 46. Each of themodules 44 and 46 include a ferrite substrate 56 and a ferrite closurepiece 58. Referring to FIG. 3, a portion of the thin film structure ofthe head is shown. The module 46 is shown in cut away section with thethin film deposited onto the substrate 56 of the module 46. Twomagneto-resistive (MR) read elements 60 and 62 are shown deposited ontothe substrate 56. One thin film write coil 64 is shown positionedadjacent to the MR elements. The transducing gap of the ferritesubstrate 56 is shown at reference numeral 66. A back gap region 68completes the magnetic circuit that is energized by the write coil 64.The ferrite closure 58 (not shown) is then affixed to the ferritesubstrate 56 to complete the module 46 and thereby form the adjacentread and write elements as is shown in FIG. 2. As stated previously, themodule 44 is essentially of similar construction to that of module 46.

The steps in forming the inventive structure of the module 46 accordingto the present invention is shown in FIGS. 4A-C. In producing thedifferent thin film layers for the MR read elements 60 and 62 and inproducing the write coil 64 of FIG. 3, different thickness of layers arerequired for the operation of each. For instance, the MR read elements60 and 62 require more thin film layers and, therefore, is thicker thanthe write coil 64 which operates to write the magnetic transitions ontothe media 28. Thus, when the closure block 58 (see FIG. 2) is placedover the thin film layers, the ferrite closure will be supported by thelayers of the MR read elements 60 and 62 but will not be supported bythe write coil 64. As stated previously, this could lead to the ferriteclosure 58 bending under stress after the module 46 is closed. The totalfilm layers in the read gap are thicker than the total film layers inthe write gap. To properly read the written bits of information on thetape media 28, the write head gap 66 must not be narrower than the MRread elements 60 and 62. The problem is solved according to thisembodiment of the present invention by depositing islands of material ofsimilar thickness to the MR read elements 60 and 62 at the back gap 68region. Thus, the magnetic head 36 and especially each module 46 and 44include a back gap write island (not shown in FIG. 3) in the back gap68.

Referring now to FIG. 4A, the read tracks are defined. First aninsulation layer of silicone dioxide and/or alumina is deposited overthe entire substrate layer. The insulation layer can be a combination ofsilicone dioxide and aluminum deposited to a total thickness ofapproximately 6,000 angstroms. In the next step, the layers of the MRelements are deposited such as is shown for the MR elements 60 and 62.All of the MR elements are deposited at the same time covering theentire ferrite substrate 56 for the module 46. For the preferredembodiment of the magneto-resistive element, a NiFeRh layer ofapproximately 360 angstroms is deposited followed by a 200 angstromlayer of Ta and a 540 angstrom thickness layer of NiFe. The tri-layerfor the MR element includes the NiFe MR layer itself together with theTa isolation layer and the NiFeRh soft film bias layer. The operation ofsuch an MR element is well known in the art and will not be furtherdescribed here. At the same time that the MR elements are deposited ontothe substrate 56, the same layers are deposited onto read islands 70,write islands 72, and back gap write islands deposited into the writeback gap regions 68. This is the first portion of the leveling for themagnetic closure block to be placed over the entire thin film depositionas will be described later. A mask is used to define the read tracks andto define the different islands. The next step in the procedure is shownin FIG. 4B.

Referring to FIG. 4B, the next step is the deposition of the conductorlayers onto the read legs up to the MR element itself. A mask is used todefine the deposition of an adhesion layer of Ti of approximately 100angstroms followed by the gold conductor layer of approximately 1000angstroms followed again by an adhesion layer of 50 angstroms. Theseconductor layers are deposited over the read islands 70, the writeislands 72, and the back gap write islands formed in the back gaps 68.The MR elements according to the preferred design are center tapped and,therefore, each MR element has three conductors, two outer conductors 74and 76 and a center conductor 78. The same conductor layers aredeposited over all of the read elements, with the read elements 60 and62 shown in FIG. 4B. Next an insulation layer is deposited over theentire substrate to prepare for the deposition of the write conductorsand the extensions of the read conductors onto the read legs. Theformation of the write conductors and the further conductor regions onthe read legs is shown in FIG. 4C.

As shown in FIG. 4C, the insulation layers are chemically etched toexpose the write conductor region 80 of each of the write transducersand also to expose a portion of the read legs 74, 76 and 78 of the MRread elements 60 and 62, further portions shown in FIG. 4B. The writeconductors are then deposited together with a thicker conductordeposition onto the read legs, as shown in FIG. 4C, by depositing anadhesion layer of Ti to an approximate 500 angstrom thickness followedby approximately 9000 angstrom thickness of gold. Note that depositionof material is not placed into the write back gap regions 68 nor ontothe read islands 70 or write islands 72 The closure block 58 (see FIG.2) when affixed to the substrate 56 extends in width approximately tothe thick leg portions of the read conductors so that these thickerlayers do not affect the gap lengths between the substrate 56 and theclosure block 58. Further deposition steps (not shown) form aninsulation layer for the crossover from a pad 82 of the write conductor80 to the external pad 84. The crossovers are then deposited tointerconnect the paths 82 and 84 together with any other conductorsnecessary in order to connect the write conductors and the readconductors to the read/write network 15 (see FIG. 1). The crossovers areencapsulated into an insulation material to insulate the conductors fromthe housing and other structures of the module 46. A cross section viewshowing the resultant islands just prior to the installation of theferrite closure block is shown in FIG. 5.

In FIG. 5, an active MR section 69 of the MR read element 60 is shownconnected to the conductors 74, 76, and 78. The read island 70 is showndeposited adjacent the active MR section 69. The write conductors 80surround the back gap section 68. The write island 72 is shown at theend of the conductors 80 adjacent to what will be the active write gaparea 66 (see FIG. 3) after abrading is performed to the completed module46 which includes the ferrite closure 58. The abrading determines thecontour of the face of the module that interfaces with the tape media 28(see FIG. 3) as well as the height of the active MR section 69 of the MRread element 60. The write islands 72 as well as the read islands 70 areremoved by the abrading step.

The write back gap island in the write back gap area 68, the read island70, and the write island 72 include a layer 90 of the same material ofthe layers of the active MR read element 69, and a conductor material 92which is deposited over the conductors 74, 76, and 78 for the readelement as is shown in FIG. 4B, but does not include the conductormaterial deposited as shown in FIG. 4C. These islands support theferrite closure 58, see FIG. 2, when the ferrite closure block is placedover all of the elements deposited by the procedure shown in FIGS. 4A-C.The ferrite closure 58 becomes the second pole piece for the writingprocedure as energized by the write conductors 80. The ferrite closure58 also operates as a shield to the read elements of the MR read head 60in a manner well known to those skilled in the art.

Thus, as is disclosed herein, an improved interleaved head is shown foruse for media recording. It is, of course, understood that a singlemodule could be used with the media recording drive of the presentinvention. In the embodiment disclosed, the layers of the read elementare thicker than the thin film layers of the write element and thereforea supporting structure, the write back gap island in write back gap area68, is provided to support the supporting structure, the substrate 56and closure 58 of the module 46. The supporting structure need not bemagnetic ferrite if thin film read and write elements are provided. Itshould also be understood that supporting islands could be provided inthe read element area if the write element materials provide a largerwrite gap. The purpose of this invention being that supporting islandscan be included to provide a constant distance between the supportingstructure of a multi-gap head. Preferably, the material for the islandsis the same as that of the longer gap element. It should be furtherunderstood that the supporting islands could be only magnetic materialin order to independently vary the magnetic properties of the read orwrite gaps containing the islands.

The principles of the present invention have now been made clear in anillustrated embodiment. There will be immediately obvious to thoseskilled in the art many modifications of the structure, arrangement,proportion, the elements, materials and components used in the practiceof the invention For instance, a nickel-zinc ferrite material is shownfor use in the ferrite substrate 56 and the ferrite closure 58 for thepresent invention. It should be understood that other magnetic ferritematerial could be used such as a manganese-zinc ferrite, or non magneticceramics if the read and write thin film elements are self operational.Further, specific materials are used in the creation of the differentlayers for the thin film elements and conductors. It is well within theknowledge of a person skilled in the art that other materials could beused as well as other thicknesses, all well within the totallithographic teachings of the prior art. The different masks andphotolithographic treatments to form the different layers are also wellknown. The appended claims are, therefore, intended to cover and embraceany such modifications within the limits only of the true spirit andscope of the invention.

What is claimed is:
 1. A method for making a data transducing headmodule having one transducing gap line extending normal to the mediamovement direction, each gap line including a plurality of alternatingwrite and read gaps, said method comprising the steps of:providing asubstrate made of a magnetic ferrite material; depositing an insulatinglayer on said substrate; depositing patterned magneto-resistive layerson said insulating layer to produce a plurality of magneto-resistiveread elements at the read gaps and produce back gap write islands;depositing a patterned conductive layer on each depositedmagneto-resistive layers and over the islands; depositing a patternedsecond insulating layer on each pattern conductor layers such that thewrite track and the read leg regions are exposed; depositing a read anda write conductor onto each patterned write track region and read legregion; depositing a read and a write interconnecting layers to connecteach read and write conductor to a data transmitting means; and adheringa magnetic ferrite closure piece covering all of the plurality ofalternating write and read gaps of said transducer, said magneticferrite closure producing a first write pole piece and a read gap shieldand said substrate providing the second write pole piece; wherein saidback gap write islands provide at least mechanical support for saidmagnetic ferrite closure piece for the write gap length.
 2. A method formaking an interleaved magnetic head comprising the steps of:obtaining asubstrate of a magnetic ferrite material; depositing materials to form aplurality of thin film read transducers; depositing the read transducermaterials in alternating positions between the read transducer toproduce back gap write islands; depositing an electrically conductivematerial to provide electrical connections to the deposited readtransducers and on the deposited back gap write island and to produce aplurality of write coils at positions alternating with the depositedread transducers and around the deposited back gap write islands;obtaining a closure of a magnetic ferrite material; and affixing theobtained closure to a surface of the substrate containing the depositedmaterial, said islands providing at least mechanical support for theclosure relative to the substrate for the plurality of write gap lengthsproduced at the plurality of write coils.
 3. A method for making aninterleaved magnetic head as defined in claim 2 wherein the steps ofdepositing materials to produce the deposited back gap write islands,also produce deposited read gap islands adjacent to the deposited readtransducers and write gap islands adjacent to the write gaps produced bythe substrate and closure, and the write coils, and further includingthe step of abrading the affixed closure and substrate at the edgeadjacent to the deposited read and write gap islands to remove thedeposited read and write gap islands, and to place the deposited readtransducer and write coils in correct magnetic transducing position.